PP.30.10] INFLUENCE OF URINARY SODIUM AND POTASSIUM EXCRETION ON BLOOD PRESSURE IN CAMEROONIAN PYGMIES AND BANTUS

Abstract

Objective: High dietary salt increases blood pressure (BP) and is a leading cause of hypertension. This study aimed to examine association between urinary sodium and potassium excretion with BP among Cameroonian pygmies under hunter-gatherer subsistence mode and Bantus, living in urban area under westernized lifestyle. Design and method: We randomly enrolled 150 Pygmies living in the Lolodorf municipality (rural area) and 150 Bantus living in Douala (urban area). Height, weight, body mass index (BMI), waist circumference (WC), BP and single overnight spot urine samples were obtained. Brachial systolic BP (SBP) and diastolic BP (DBP) were measured in triplicate using an automatic device (Omron 705 CP). Urinary sodium and potassium concentration was determined by flame photometry and was used as surrogates for salt intake. Results: As Compared to Bantus, Pygmies were shorter with a lower body weight (all P < 0001) and had a lower age-standardized prevalence of hypertension (3.3 % vs 28 %) (all P < 0.0001). Age-adjusted SBP and DBP were lower in Pygmies than in Bantus (all P < 0.001). Both SBP and DBP increased with age but to a lesser extent in Pygmies (both P < 0.01). Urinary sodium excretion was lower in Pygmies than in Bantus (46.9 ± 32.4 vs 121.5 ± 61.0 mmol/L, P < 0.0001). Age-adjusted SBP and DBP were positively associated with urinary sodium concentration in Bantus (all p < 0.05), but not in Pygmies. In the two groups, urinary potassium concentration was similar, and was not related to BP (all >0.05). In the whole study population and in Bantus taken separately, urinary sodium excretion was higher in hypertensive than in normotensive subjects (P < 0.0001). Multivariate logistic regression analysis showed that urinary sodium excretion, Bantu status and age are independent determinants of hypertension in the whole study population (P < 0.0001). Conclusions: The present study demonstrates that hunter-gatherer living is associated with low level of urinary sodium concentration which likely explains the low rates of hypertension and slower increase of BP with age in traditional pygmies. Hypertension is more common and urinary sodium concentration is higher in Bantus. Urinary salt excretion emerged as an independent predictor of hypertension in this Cameroonian population.